The Sigma 70mm F2.8 EX DG Macro is a large aperture medium macro lens designed for use on full-frame and APS-C format digital SLRs. Three SLD (Special Low Dispersion) glass elements provide optimum color correction and sharpness throughout the entire zoom range and Super Multi-layer coating reduces flare & ghosting. A floating internal focus system enables a minimum shooting distance of 7.4 inches, and maximum reproduction ratio is a 'true' macro 1:1. It has a reputation for being one of the sharpest lenses on the market, but autofocus is slow.